At present, techniques of electrical separation have found a broad field of applications in industries, either as a final operation of a treatment technology, or as a preparatory operation for concentration processes. All the electrical separators are of the single-feed kind which puts definite restraints on their productivity.
Therefore, so far an increased throughput of drum-type electrical separators has been attained either by extending the length of the drum where the separation takes place or by providing a multi-unit separator assembly where several separators are arranged in horizontal and vertical rows, with the resulting loss of floor area, design and maintenance complications.
There is known an electrical drum-type separator for separating a mixture of electrically conductive and non-conductive materials (A. V. Degtyarev et al., "Separatorshchik elektricheskikh separatorov", Nedra/Moscow/ pp. 27, 28, 54), comprising a housing having mounted therein a rotatable drum serving as a collecting electrode, means for feeding a mixture of loose materials onto the peripheral surface of the drum, a corona-discharge electrode for applying an ion charge to particles of the mixture of loose materials in an electric field produced between the electrode and a portion of the peripheral surface of the drum, spaced from the peripheral surface of the drum, a brush for sweeping non-conductive particles off the surface of the drum, mounted behind the corona-discharge electrode in the direction of rotation of the drum, and receptacles arranged in the respective paths of electrically conductive particles, aggregations of conductive and non-conductive particles, and non-conductive particles.
In this known electrical drum-type separator the drum is so arranged that its axis of rotation extends horizontally, the means for feeding the mixture of loose materials onto the peripheral surface of the drum including a feeder having a feeding slit extending along the generatrix of the peripheral surface of the drum. Arranged intermediate the corona discharge electrode also extending along the generatrix of the peripheral surface of the drum and the brush is an electrostatic electrode extending parallel with the corona-discharge electrode. The receptacles arranged in the respective paths of electrically conductive particles, aggregates of conductive and non-conductive particles, and non-conductive particles, underlie the drum.
The corona-discharge electrode, the electrical electrode, the brush for sweeping electrically conductive particles off the peripheral surface of the drum in combination with the portion of the peripheral surface of the drum, lying therebetween, define a separation zone where the separation of a mixture of loose materials takes place.
The throughput of this known electrical drum-type separator is predominantly dependent on the length of the drum serving as the collecting electrode. A certain increase in the throughput can be also attained by stepping up the diameter of the drum, because in this case the drum can be rotated at a higher peripheral speed without non-conductive particles being thrown off its peripheral surface by the centrifugal forces acting upon the particles when the drum revolves. However, this approach to increasing the throughput of a separator results in its overall dimensions being increased, and the area of the peripheral surface of the drum not taking part in the separation process also increasing, this area amounting to at least one third of the entire peripheral surface area of the drum.
With the drum of the known separator extending horizontally, a mixture of loose materials can be supplied only to one portion of its peripheral surface, so that the process of separation is carried out in a single separation zone irrespective of the drum diameter.
From engineering design considerations, the length of the drum of the known separator would not be made greater than some 3000 mm, and its maximally attainable throughput is about 1.5 m.sup.3 /h of feed material.
The aforementioned multi-unit arrangement of drum-type separators into a separation unit requires a complicated mechanical system of driving several drums, which complicates both the design and operation.